The invention relates to a self-sealing closure for mailing bags, letter envelopes, sacks, etc. where, on the inside of the flap and on an edge zone of the backside, strip-like, dry latex, synthetic resin or adhesion gum coatings are applied.
Such self-sealing closures are known as permanent sealing closures for sealed first-class letters and as temporary sealing closures for printed matter. There are also known combination letter and printed matter closures which can be used as desired. For example, both closure surfaces are coated with a mixture of latex and synthetic resin dispersion which in the dry state are arepeatedly usable printed-matter closure, and in the wetted state a permanent first-class letter closure. This closure has the disadvantage that, to produce the solid first-class letter closure, a closure surface must be wetted with water, where setting times for the sealing must be observed, and the superior self-sealing method can be used only for the printed-matter closure.
With another known combination first-class letter and printed-matter closure for a double-wall mailing bag, one closure flap section has openings through which the inside of the other closure flap section is provided with dot-like sealing locations. These dot-like sealing locations, to form a printed-matter closure, can be brought into sealing contact with the backside of the mailing bag or envelope. To form a solid first-class letter closure, additional strip-like sealing areas are required on the inside of the inner closure section. Thus the solid first-class letter closure has the disadvantage that only the inner closure flap section can be connected solidly with the backside while the outer closure flap section comes into printed-matter closure contact with the backside of the mailing bag or envelope only via the dot-like sealing areas and thus is easily opened, making the inside of the mailing bag or envelope easily accessible.
It is the object of this invention to provide a self-sealing closure for mailing bags, envelopes, sacks, etc. which, without moistening, by means of an identical sealing coating on the inside allows a choice between a solid first-class letter closure of high sealing strength and a low-postage printed-matter closure which can be easily opened because of low sealing strength and, after postal inspection, can be closed again.